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Ruby ActiveRecord Basics Migrations and Relationships Looking at our Application

Posted by Sebastian Velandia
Sebastian Velandia
24,676 Points

How the total cost is calculated?

Hi Im trying to understand the project that is in the video, and in the line 4 of accounts/show.html.erb

Total Cost: <%= (@account.account_entries.map &:cost).sum %>

Im really lost with the way that total cost is calculated I do not understand the .map neither the &:cost and what is returned within the pharentesis? (...).sum

Thanks for your explanation

1 Answer

Maciej Czuchnowski
Maciej Czuchnowski
36,441 Points
Maciej Czuchnowski
Maciej Czuchnowski
36,441 Points

.map will go through every account_entry for the given account, take the cost attribute, return an array of all these values and then .sum will add all of them together and return the final result. I believe that &:cost tells map to only look at the cost attribute an dignore all other things.